This is a tricksy situation. I know for a while my sweetie was sabotaging my efforts--unintentionally. We were used to eating junkie foods or using food to celebrate etc. We've talked about it and this isn't an issue anymore for me but one of the things I suggest to you is, in addition to packing your lunch and other stuff that's been suggested... propose other things he can do for you to be nice. Because, buying food for someone is a way of taking care of them (however unsupportive the choices might be) so maybe suggest NON FOOD treats that you'd like. So, you could tell him, instead of food how about roses, or it would be fantastic if you could bring me home some yummy lotion instead of fish and chips... If he tells you he is stopping by a restaurant you can ask him to bring home a salad for you, or a kid size meal. This might help. Talk with him openly as others suggested and explain that he is indeed sabotaging your efforts to be slimmer and healthier!
Ultimately it's up to you to not allow your efforts to be sabotaged. Plan ahead, take your lunch with you, eat before he gets home with fish and chips, have healthy snacks with you at all times... you can also plan ocassions when you will indulge and tell him when that time is. That way you can enjoy the less healthy options with him and avoid derailing your efforts. IT could also give you something to look forward to, a fun Date! It makes it easier sometimes to know that it's not that you'll never eat that stuff together, it's just going to be a treat rather than routine!
He can only sabotage your efforts if you allow him to. So, unfortunately the burden of responsibility is on you. If he persists in bringing home the chips, find a way to resist them. Stop thinking of it as depriving yourself of those foods. You are making healthier choices and you can refuse to let those foods control you. After a while of not eating greasy fried foods, many people lose their taste for them, I know I have. I'm not saying I don't crave fries once a month
but for the most part,they just taste like fried fatty fat. Yuck! LOL
Good luck !!!